Triangular signal generator



Sept. 19, 1950 w. A. MILLER 2,522,957

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Sept. 19, 1950 w. A. MILLER 2,522,957

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Fem/m l/L RR W0 YE G E N E RRTOR Sou/10E OF T/m/va 0R INDEX M/ZRKPatented Sept. 19, 1950 2,522,957 7 TRIANGULAR. SIGNAL GENERATOR lWilliam A. Miller, Port J efiersorl Statiom'N'. Y),

assignor to Radio Corporation of America, a corporation of DelawareOriginal.application June 27,, 1942-, Serial No.

, diiced Waves or pulses is triangular.

tion is a division of my co-pending applicatiom.

448,804. Dividedand this application. Februan 6, 1946, Serial No.6453911- I Claim;

. 1 I The present invention relates to" signalgenerators and moreparticularly, although not neces'-- sarily exclusively, to generators ofalternating currents or pulses of triangular form. The invention isapplicable to the production of voltage waves orpulses and current'wavesor pulses flowing' as a result of voltages generated in accordance withthe invention. The form of-the pro- Thisinven- Serial No. 448,804; whichwas filed June 27, 194-2, now' Patent No. 2,413,063, granted December24, 1946. l

One object of the present invention is topr'ovine a generator oftriangular wavesor triangular pulses; in which a desired degree. ofcontrol can be: given toeitherslopeof the triangular wave.

. Another object is to provide an improvedgenerator oftriangular pulses:which repeat themselves at specified and controlled. intervals of time;but which pulses occupy a time interval" less than. or. small comparedto the repetitionrate.

A further object: is: to provide a generator. of triangularwaves orpulses, utilizingrconstant current: devicesaboth. for charging. anddischarging a chargestoring element.

still further object is. to provide a generator oftriangular waves orpulses, in which the: return slope of the wave or pulse is delayed. overa? desiredinterval of time.

Signal generators embodying features of the invention are especiallyuseful i'n a cathode: ray oscilloscope system which enables the signaltobe measured: toappear. on; the forward trace of the sweep; and the.index .or timing mark to? appear ,onthe-returntrace of the sweepswithoutith'e' need of: switching devices.

Qther and more specific objects of the inventionwillebecomeapparent andsuggest themselves to: those skilled in the art towhich the inventionis. directed upon. reading the following specifics. tion. and claim. inconnection with the drawings in which:

' Fig. l: graphically illustratesknown practiceinyolving the-use of a.sawtooth-wave for-m applied total. cathode ray oscilloscope: formeasuring purposes; 1 g p Eigl 2. graphically illustrates the. useof,atriangular. wave with adelayed. return slope for applicationto acathoderay oscilloscope;

Eig. 2a. graphically illustrates aseriesofitriang-ular pulses whichareproduced. by several. generators. of thepresent invention, which pulsescan bemadeto repeat themselves. at specified and controlledintenvalsoftime; p

ill

Figs. 3; 4, 5,511, 6 and fiu show'seve'r'al embodiments of generatorcircuits in. accordance with, the invention, for producing triangularwaves of thekin'd. illustrated" inFig. 2

Figs; '7' and 8 showgenerator circuits in accordance with two otherembodiments of the present invention, for producing triangular pulses ofthe kind illustrated in Fig. 2a; and

Fig. 9' illustrates, schematically; a simple circuit arrangement usefulin radio" locating systems for applying; the signal pulse to be measuredto the signal plates of an oscilloscope" during the forward trace ofthe" sweep and the-index or timing marks to the same signal platesduring return trace-of the sweep.

Heretofore; in using cathode ray Oscilloscopes as measuring orindicating instruments, it has been customary to impress timing or indexmarks or other signals on the trace of the cathode ray beam. Accordingtoknown practice, this has been-accomplished'by applying a sawtooth waveto the'hori zontal deflecting plates of the oscillo' scope,- andi thenalternately impressing the signal to be: measured and the index ortimingmark on the forward traceot the cathode ray beam. Toachievethe-alternate application of the signal and the. index marka-tc:the forward trace of the cathode. ray oscilloscope. there: have beenemployedl mechanical: or electronic switching devices. Eig. 1.illustrates graphically known prac tice, wherein a sawtoothwwavez of thetype shown this figure is. appliedzt'crthe horizontal deflecting. platesof. the: cathode ray oscilloscope, while the. signal to be measured. orunder observation, hereinli'ndicated as a pulse I'D, is applied: to thesignal deflection. plates for observation on the forward trace of the:beam, while the index or timing; marks, herein; represented as H, are applied to the'same'signal' deflection plates for observation on the nextforward trace of the (Bathe. ode ray beam. The sawtooth wave, as iswellknown, allows the; cathode ray beam to be de-:- fiectecl atauniformr rate over the surface of the screen. of theoscilloscope,during. the time To and '31, after which the spotisrapidly returned to.its original position. during the time T1 and T2. Thisllatter-timeisordinarily made to be as short as possible consistent with stability.Actually, the. sawtooth wavaof Fig. 1. represents the-voltage usuallyonthehorizontal sweep plates, the cathode. ray trace being only ahorizontal Know the oscilloscope. The: two voltages, it e., the signalto -bemeasured and the: index or timing marks; bothof which are: tobe'observedlare impressed according to known: practice: alternately on.the

same signal deflection plates of the tube by means of some mechanical orelectronic switching device. One difliculty with this known practice isthat the switches, both mechanical and electrical, are complicated, andthe mechanical switch requires synchronization to prevent accidentalchopping. The electronic switch, furthermore, requires a great number oftubes and several channels, in addition to also requiringsynchronization.

The inventio claimed in my copending application, Seria1 No. 448,804referred to above, overcomes the foregoing difiicultyby eliminatingtheneed for switching arrangements in applying the signal to be measuredand the timing marks on the oscilloscope. invention claimed in thepreviously mentioned copending application, it is proposed to delay theAccording to one feature of the index mark with any of the pulse marksto be identified may control a rheostat or a potentiometer applyingpotential to a tube, and may be suitably calibrated to read thedistance. For a more detailed understanding of the principles of theradio locating system generally referred to above, reference is made tocopending Hansell application Serial No. 427,266, filed January 19,

return time or slope of the sawtooth wave, in

order to form a triangular wave of the type shown in Fig. 2, forapplying a voltage on the horizontal sweep plates of the oscilloscope,as a result of which the signal to be observed can be applied to thevertical signal plates, while the cathode ray beam is moving in onedirection (the forward trace, for example), and the index or timingmarks applied to the same 'vertical signal plates, while the cathode rayspot is moving in the opposite direction (return trace). Thus, if thetriangular wave of Fig. 2. represents the voltage which applicantapplies to the sweep plates of the oscilloscope, the signal pulse to beobserved (herein labeleld ID) will appear on the surface of theoscilloscope screen during the time To and T1, while the index ormarking pulses H will appear on the surface of the oscilloscope screenduring the time T1 and T2. As mentioned above, in practice the traceappears only as a horizontal line on the oscilloscope, although thetriangular shape of the sweep voltage curve represents the voltage curveof the wave applied to the sweep plates. It will be understood, ofcourse, that although sweep plates only have been mentioned,presupposing the use of an electrostatic deflection type ofoscilloscope, it should be understood that the methods mentioned aboveare applicable to magnetic-deflection oscilloscope tubes usingdefleeting coils instead of plates. A simple circuit for achieving theresults graphically shown in Fig. 2 is schematically illustrated by wayof example in Fig. 9 described later.

A triangular wave. impressed upon the'sweep plates of a cathoderay-oscilloscope measuring or indicating instrument is useful in theradio locating field. Such a wave may be readily produced in accordancewith the pres'ent'invention.

For example, in the radio locators commonly employed for militarypurposes, the pulse is sent out by the transmitter and reflected fromthe object to be detected, which might be an airplane or a ship. Thisrei'lected'pulse will appear on the forward trace of the oscilloscopesweep, while the index markings will'appear on the returning trace ofthe oscilloscope sweep. The time of the trace of the sweep wave fromthebeginning of the trace (started by an outgoing pulse) to the peak ofthe sweep voltage, corresponding to thefurthest distance of the traceonthe oscilloscope before the trace returns, is made to be slightlygreater than the time for a pulse to reach an object in the greatestdistance range to be observed and then return as an echo or reflectedpulse. Due to the persistence of vision, the reflected pulses and indexmarks will both appear to the eye on the oscilloscope screenat the sametime; By

1942, now PatentNo. 2,455,673, granted December 7, 1948, and a copendingLindenblad application Serial No. 441,311, filed May 1, 1942, now PatentNo. 2,411,410, granted November 12, 1946.

Fig. 2a. illustrates another type of triangular wave herein shown astriangular pulses separated from one another which can be efiectivelyproduced in accordance with the present invention. The triangular pulsesof Fig. 2a repeat themselves at specified and controlled intervals oftime, and the pulses occupy a time interval less than or small comparedto the repetition rate. When using the triangular pulses of the typeshown in Fig. 2a, the time interval To to T1 may, for example,correspond to the time it takes for a signal of a radio locating system,when such pulses are applied to such a system, to go out to the maximumdistance range to be observed and then return as an echo. Thispresupposes, of course, that there is an object in this distance rangeto be detected, in order to reflect a wave to produce a reflection orecho pulse. The time T1 to T2 is a variable time, which can becontrolled in accordance with the invention, in which the index ortiming marks may be made by suitable circuits. The time between thebeginning of any two adjacent triangular pulses represents the timebetween the initiating pulses. The several embodiments for producingwaves or pulses of the type shown in Fig. 2a, will be described later inconnection with the generator circuits of Figs. 7 and 8.

The different generator circuits of the present invention for producingtriangular waves of the type shown in Fig. 2 will now be described: Suchgenerator circuits are shown in Figs. 3, 4, 5, 5a, 6 and 6a.

Fig. 3 shows a simple circuit for producing the triangular wave of Fig.2. In this system the circuits L1, C2 and L2, C3 comprise constantcurrent networks. The condenser C1 and the series circuit R2, C3 arecharged by current flowing through L1 and R1 from a source of positivehigh direct current voltage HT. The values of C2 and L1 are so chosenthat for the particular frequency desired, a constant current flows inthe condenser C1, so that the voltage across the terminals of C1increases linearly with time. Putting it in other Words, the magnitudeof current which flows in C1, B2, and C3 is determined by the values ofL1, C and L2, C3. The resistors R1 and R2 serve to present reactionbetween the two constant current networks L1, C2 and C3, L2. Theseconstant current networks are resonant to the particular frequency ofthe sweep desired on the deflection plates of the oscilloscope, to whichthe output of the system may be applied. A gaseous discharge tube I isshown having its anode connected to one terminal of the coil L'z'ofone'of-the constant curirent networks.

the fact that the heating of the elements of the system may change thetime constants and the tuning of the constant current networks L1, C2

andLz, C3. The magnitude of the resistor R3 of the synchronizationcircuit is made reasonably high to prevent the synchronization circuitfrom interactingwith the grid control of the gas triode.

The condenser C4 is an isolating (blocking) con- -denser to prevent thevoltage on the grid of the triod'e from entering the synchronizationcircuit, and vice versa. Returning now to the operation of the system ofFig. 3, the gas triode I will ionize and-cause current to flowtherethrough when .the

#ungrounded terminal of the storing condenser C1 reaches aparticularpotential, at which time the condenser C1 will discharge throughtube I.The circuit constants L2 and C3 are so chosen that a labeled sweepvoltage has the form of Fig. 2.

The repetition rate of the triangular voltage Waves or frequency may bekept constant despite temperature changes by the application of thesynchronizing pulse applied to the grid of the gas triode I as mentionedabove.

I The output of the system of Fig. 3 is available at the terminalsmarked sweep voltage and can be applied to suitable deflection plates onthe oscilloscope. This repetition rate of the triangular wave'shou'ld be'a'multiple of the frequency of the signal to be observed. Incidentally,it should here be noted that the coil L2 of Fig. 3 may or may not havean iron core, depending upon the frequency of the sweep desired. 1Although a gaseous tube has been shown used in Fig. '3, it should beunderstood that, if desired, other types of electron discharge devicesmay be employed, such as a high vacuum discharge device which mightbe adynatron oscillator or a blocking oscillator or even a multivibratoroscillator. i

"Fig; 4 shows another embodiment of the invention which is amodification of Fig. 3, differing 'iromFig. 3 primarily in the use of aconstant current pentode tube P, in place of the constant :currentnetwork L1, C2 of Fig. 3. The high vacuum electron discharge devicepentode P is biased in such away by variable resistors R1 and Re, thatits cathode current is essentially independent or the voltage appliedfrom ET. This cathode current is' used for charging the condenser C1.The condenser C5 in Fig. 4 is a bypass condenser, and serves toke'ep thesignal off the screen grid of tube P. The constant current network L2,C3 and the gas triode circuit l are similar to the samenumbered circuitelements of Fig. 3, and operate in substantially the same way.

Although the systems of Figs. '3 and 4 show ways of producing atriangular waveof the type "shown in Fig. 2, these generator'circuitsare not preferred because of the following difliculties whichtheyexperience. These difficulties are 'caused by'the use of passivenetworks to control =thecurrent, and are briefly (1) the constancy bgfthe'current depends upon the ability of the coil to produce extremelyhigh voltages at reso name, and such high voltages require a very high"Q circuit which is rather difficultto obtain; .(2)

the operation of such circuits depends upon resonancewhich requires thata new circuit be used for each frequency desired; and (3) a Fourieranalysis of a triangular wave reveals that there are many harmonicspresent and a condition of resonance for the fundamental frequency meansthat the currents for the harmonics are not constant, as a result ofwhich there is a departure from linearity in the output voltage wave.

The foregoing difficulties mentioned above in connection with Figs. 3and 4 are overcome by the generator circuits of the invention of Figs.5, 5a, 6 and 60.. These last four figures illustrate circuits whichavoid the use of passive networks to control the current, and, insteadof passive networks, employ electronic devices for producing constantcurrent flow in both the charge an discharge parts of the cycle.

Fig. 5 differs from Fig. 4 in the use of a temperature limited diode 4,which replaces the constant current network L2, C3 of Fig. 4. It shouldbe noted that Fig. 5 employs substantially the same constant currentpentode charging circuit shown and described in connection with Fig. 4.The temperature limited diode 4 is designed 'to Work onthe saturatedportion of the plate voltage-plate current curve for a particular valueof cathode temperature. Preferably, a curve is selected in which theplate voltage range for constant current is rather large. The system ofFig. 5 can be employed to produce a triangular wave of isoscelesconfiguration; that is, one in which the percentage of the periodrequired for the charge and discharge is the same. The charging time ofthe triangular wave generator Fig. 5 (and this also applies to thesystem of Fig. '4) can be controlled within desired limits by variationof the values of the resistors R1 and R6.

Fig. 5a is a modificaion of Fig. 5, anddiffers from Fig. 5 mainly in theuse of a constant current pentode tube P to replace the temperaturelimited diode 4. This pentode P is designed to function in a mannersimilar to the operation of constant current pentode P, and hasassociated therewith resistor R6, condenser C, and resistor R1,whichcorrespond to resistor R6, condenser C, and resistor R1 of pentodecircuit P. The use of the pentode P enables a control in percentage ofthe period required for the discharge. Thus, by means of the system ofFig. 5a, I am able to obtain any desired wave shape for the tri-.angular output wave, with any desired control of the charge anddischarge time of the pulse available at the sweep voltage terminals.

Fig. 6 is a generator of triangular waves, and is substantially similarto the circuit of Fig. 5, except that the positions of the temperaturelim-- ited diode and the gas triode are reversed. In Fig. 6 thecondenser C2 is charged through the temperature limited diode 4', whilethe constant current pentode P" prevents a more rapid discharge of thecondenser C1 through the gas triode 1 than the time of charge of thiscondenser. The rates of discharge in the system of Fig. 6 can becontrolled by the adjustment of the resistors Re" and R1". In this wayagain we can obtain an unsymmetrical triangular wave. 7

Fig. 6a shows a triangular wave generator which differs from Fig. 6primarily in the use of a constant current pentode P for the temperaturelimited diode 4' of Fig. 6. Thus, Fig. 6a employs ity.

612. enable a control of the time of discharge of the condenser C1through the gas tube, through adjustment of the resistors in the circuitof the pentode in the discharge path. Also, temperature limited diodesas shown in Figs. 5 and 6 have to be operated at reduced cathodetemperature which makes the device very sensitive to fluctuations in vthe supply voltage to the cathode heater. Hence,

temperature limited diodes are to be avoided where such fluctuations areto be expected.

Figs. 7 and 8 show preferred arrangements for generating triangularpulses of the kind shown in Fig. 2a. The systems of these two figureshave the advantage of being able to produce triangular pulses which areinitiated by the synchronizing pulse. For this reason they are welladapted for use with the radio locating system hereinabove described,although not limited thereto.

Referring to Fig. 7 in more detail, there is shown a multivibrator ortrigger circuit comprising vacuum tubes T1, T2, and anothermultivibrator or trigger circuit comprising a pair of electrodestructures, included in a single evacuated envelope T4. The storing orcharging element comprises a condenser C1, which is charged through avacuum tube T3, the latter in turn being controlled by the multivibratorcircuit T1, T2. The condenser C1 is discharged in a manner describedlater through the pentode electrode structure of the multivibrator T4.The grids of the two multivibrator circuits are biased unsymmetrically,one grid having a negative bias applied thereto, while the other gridhas an adjustable resistor connected to the ground. In eachmultivibrator circuit, the anode of each electrode structure iscross-coupled to the grid of the other electrode structure, so that thecircuit as a whole has one degree of electrical stabil- In the operationof such a multivibrator, there is a predetermined maximum anode currentflow in one of the electrode structures, and a predetermined minimumanode current flow in the other electrode structure, or the reverse, thechange being controlled by a pulse of desired potential applied to thegrid of one of the electrode structures. Referring to the multivibratorcircuit composed of tubes T1 and T2, the anode of T1 is coupled to thesignal grid of T2 through resistor and condenser combination M, whilethe anode of T2 is coupled to the grid of tube T1 through a condenserC6. The input circuit which provides the initiating pulse is coupled tothe grid of T1 through a condenser N. The tubes T1 and T2 are such thatnormally, in the absence of an initiating pulse of negative polarity,tube T1 is conductive and tube T2 non-conductive. The application of anegative impulse to condenser N will impress a negative pulse on thegrid of tube T1, which causes a change in the anode current of tube T1and simultaneously therewith a change in the anode potential of thissame tube. This same change is immediately augmented by the consequentchanges in the grid and anode potentials on the tube T2. The reason forthis follows: A decrease in the anode current of T1 caused by theapplication of a negative potential to the grid of T1, will place apositive bias on the grid of T2, thus causing current to flow into T2.The How of current in T2 in turn will cause a lowering of the voltage onthe anode of T2, as a result of which the condenser C6 will be chargednegatively, and the current of tube T1 will be further decreased untilcurrent saturation of tube T2 is reached, at which time tube T1 will benon-conducting and tube T2 conducting. This condition obtains as long asthe negative charge remains on condenser C6. The length of time thecharge remains on condenser C6 is determined by the adjustment of theresistor R7, as well as by the value of Ce. If resistor R1 is small, thecharge on Co will leak ofi rapidly. As a result of the foregoing actionof tube T1 becoming non-conductive and tube T2 becoming conducting, acondition the reverse of that previously existing, there will be apositive potential pulse on point A and a negative potential pulse onpoint B.

When the charge on condenser Ce has leaked off, the tube T2 will againbecome non-conducting and tube T1 conducting, thus restoring themultivibrator to its original condition of stability. The value andadjustment of resistor R: will determine the time it takes tubes T1 andT2 to be restored to the normal condition of stability in which T1 isconducting and T2 non-conducting, and determines the width of the pulsesavailable at the anodes of tubes T1 and T2 at points A and B,respectively. Thus, it will be seen that from an initiated pulse appliedto condenser N, there are obtained two pulses of voltage, controllablein width and out of phase; The time delay between initiating pulse andfinal saturation is determined by the rate at which the voltages at Aand B can charge Cs, Cm and the input capacitances of tubes T2 and T1,respectively; that is, Ea must charge T2 and Cm, while Eb must charge T1and C6.

The voltage pulse from tube T1 is positive in sign; very steep-sided,and flat on top. This pulse is applied through the coupling condenser Coto the anode and screen grid of tube T3. Normally, tube T3 isnon-conducting in the absence of a positive pulse applied to its anodeand screen grid by tube T1 over condenser Cc. The application of apositive pulse to the anode and screen grid of tube T3 causes it to passa current to charge the condenser C1 at a constant rate. The resistorsR8, R9 and R10 are adjusted in such manner the tube T3 charges thecondenser C1 at a constant rate, for the duration of the charge is, ofcourse, controlled by the resistor R1 and condenser Ca in themultivibrator circuit T1, T2.

The multi-vibrator circuit T4 operates somewhat similarly to themultivibrator circuit T1, T2, the former being shown as one tube ratherthan two tubes, merely in the interest of economy. The triode orleft-hand electrode structure portion of T4 is normally conducting,while the pentode or right-hand electrode structure portion of T4 isnormally non-conducting. During the cycle of operations of themultivibrator T1, T2, the negative pulse from point B on the anodecircuit of tube T2 supplies a negative pulse to the differentiatorcircuit constituted by condenser C13, R13. This differentiator circuitwill produce from the flat topped negative pulse supplied thereto, botha sharp negative pulse and a sharp positive pulse separated by the widthof the pulse from T2, the negative pulse of which has no effect, but thepositive pulse of which acts on the first grid of the pentode electrodestructure portion of T4, to cause this electrode structure to passcurrent. The drawing of current by the pentode section-of T4 will stopthe current flow in the-triode section of T4 ina manner which will bequiteiapparent from what has been previously stated connection with themultivibra-tor cir cui-t .T1, T2;., Resistor R11 is one ofthe elementspath to; discharge condenser C1. After a period of time determined byresistor R14 and condenser; C14,;current flow between the cathodeandscreengrid; of the pentode section will, cease, and the dischargecircuit for condenser C1 is then ready for the next pulser Condenser C12is merely a bypass circuit. It will thus be seen that the cycle ofoperations of the multivibrator circuit T1 and Tz produces' two flat toppulses, one of which controls the charging of condenser C1 and the otherof which controls the discharge of the condenser C1 after this condenserhas been charged to a desired value. The value of condenser Cs andresistor R7 determines the Width of the flat top pulses produced bymultivibrator T1 and T2, and hence the duration of the charge applied ata constant rate to the condenser C1. The value of condenser C14 andresistor R14 of the multivibrator circuit T4 determines the period oftime of the discharge through the pentode section of T4, while resistorR11 aids in determining the rate of discharge.

The operation of Fig. 7 produces a triangular pulse, of nearly the shapeshown in Fig. 2a. It has been found that departure from strict linearityon the discharge half corresponding to the return slope of thetriangular wave, was tolerable, thus resulting in considerablesimplification of the circuit. If strict linearity on the discharge partof the triangular pulse is desired, this can easily be obtained by theuse of another constant current tube controlled by the discharge pulsefrom multivibrator T4. Such additional constant current tube can beinserted in the connection between the condenser C1 and the anode of thepentode section of T4, and may, if desired, comprise a temperaturelimited diode of the type shown in Figs. 5 and 6. It is estimated thatthe circuit of Fig. 7 will produce a sweep voltage at the terminalslabeled such, which starts within 0.1 to 0.05 microsecond after theleading wave front of the initiating pulse is impressed on the controlgrid of tube T1. Although the system of this figure has been describedparticularly in connection with producing a series of triangular pulsesof the type shown in Fig. 2a,

which repeat themselves at specified and controlled intervals of time,and. which occupy a time interval less than or small compared to therepetition rate, it should be understood that, if desired, this systemcan produce a triangular 7 wave of the type shown in Fig, 2 by suitableadjustment of resistors R1, R8, R9, R10, and R11.

Fig. 8 shows a generator of triangular waves which is more stable thanthat shown in Fig. 7 and is to be preferred. In Fig. 8 the functions ofthe multivibrator comprising tubes T1 and T2 are identical with the samenumbered tubes in Fig. '7. The multivibrator circuit T4, T4" of Fig. 8functions in a manner similar to the multivibrator circuit and can besaid to some extent to be like that of T4 of Fig. '7, except that inFig. 8 two tubes are used. The positive pulse from tube T1 of Fig. 8,however, is now applied through coupling condenser Ct to a suitable gaincontrol circuit-, lier'e shown asa" resistor R15, from" which a,voltage'isapplied" to the first grid of the vacuum tube T3. It should benoted that thecondenser C1 is here charged through the tube T3 thecharging current for this condenser beingsuppliedby the high voltagesource HT, instead of from tube T1, as in Fig. 7. The advantage of thisparticular arrangement is that the system is made. less sensitive tovariation in tube characteristics. The multivibrator circuit comprisingtubes T4; T4 assumes the function of T4 in Fig. 7, but the two powertubesof Fig. 8 give amore rapidly acting discharge circuit, whichpreferrled i'na systemsuitable for use in connection with aradiolocating circuit. The condenser C1 of Fig. 8 discharges'throughresistor R16 and thewrightehand xpentode T4"-.: .By varying; the

value of resistor R16, we are :able; to obtain a."

change in the rate of discharge of the condenser C1. The remarksmentioned above in connection with the linearity of the dischargecircuit of Fig. '7 apply equally Well for the circuit shown in Fig. 8. 1

Fig. 9 shows, schematically and partially in block form, a circuit forusing the pulse-initiated triangular wave generator. The initiatingpulse arriving from a radio locating pulser makes the generator I08start through its cycle of operation producing a triangular pulse at theoutput terminals Z of the generator. This pulse is applied to onesweeping plate of the cathode ray tube and load resistor R1 through asuitable blocking condenser C1. Since the sweep voltage is produced withreference to ground, and since the other sweeping plate of theoscillograph is sensibly grounded through resistor R2 (R2 may be zero),the cathode ray is deflected across the fluorescent screen of the tubeCRO. Any echo signals to be received are impressed on signal plate I ofCR0 while the spot is moving away from its rest position by means of thevideo amplifier shown (or other device) through blocking condenser C2and load resistor R3. When the spot has reversed its motion and isreturning toward its rest position, the marking device, which is phasedwith respect to the video circuit or initiating pulse (as shown), inorder to prevent its operation during reception of a signal pulse, thenimpresses the marking pulse on load resistor R4 and signal plate 2.

It should be distinctly understood that the triangular wave ortriangular pulse generators of the invention described above inconnection with Figs. 3 to 8, inclusive, may have wide application andare not limited to use in radio locating apparatus, herein given aboveby way of example as one application. As an illustration, the sweepsignal of the invention may be used in television and in facsimilesystems, in which case it would be possible to obtain a substantialincrease in the number of lines over presently used systems withoutincrease of frequency band, because the time of retrace can be made verynearly zero, and practically all the necessary signals which arenormally transmitted and received during the retrace time in presentlyused systems (about 10%) can be sent either superimposed or in 0.1% ofthe time. The terms wave or wave form in the appended claim are intendedto apply to the non-sinusoidal variations of Figs. 2 and 2A.

Having noW described the invention, what is claimed and desired to besecured by Letters Patent is the following:

A generator of non-sinusoidal waves compris- 11 ing a charge storageelement, a multivibrator circuit having one degree of freedom forproducing flat top pulses in response to an input pulse, a

constant current circuit connected between said storage element and onepoint on said multivibrator circuit at which said flat top pulses areadapted to appear, and another multivibrator circuit connectedeffectively in series with said storage element for discharging saidstorage element at a substantially uniform rate, said last multivibratorcircuit having an adjustable element associated therewith forcontrolling the rate of discharge.

WILLIAM A. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number Number 12 UNITED STATES PATENTS Name Date Lewis Aug. 25, 1936Lewis Aug. 25, 1936 Batchelor Oct. 26, 1937 Puckle Apr. 19, 1938Schlesinger Sept. 6, 1938 Banks Feb. 21, 1939 Young Sept. 12, 1939Norton Nov. 21, 1939 Eaglesfield June 3, 1941 Urtel July 29, 1941 MooreAug. 5, 1941 Blumlein Dec. 16, 1941 Cook Jan. 30, 1945 FOREIGN PATENTSCountry Date France Aug. 1, 1938

